Hydrant Flushing FAQs

What is hydrant flushing?

Hydrant flushing is a release of water from fire hydrants. It is a controlled procedure that is vital to the general maintenance of Sun Prairie’s water distribution system.

Why do utilities flush hydrants? 

Utilities usually flush to improve water clarity, appearance, and quality by clearing settled iron and other minerals from the water mains (distribution pipes.) 

Hydrant flushing helps avoid random occurrences of rusty water if there is a large demand for water, such as during a major firefighting effort. Water mains are also flushed to physically operate the hydrant (called “exercising”) and to inspect for hydrant maintenance needs.

My water is discolored, what do I do? Image of the inside of a dry barrel fire hydrant.

Water main flushing stirs up mineral sediment that can temporarily cause yellow, brown, or reddish water

If you have discolored water:

  1. Go to a faucet in the lowest level or your home or business, like a basement utility sink or first floor bathtub.
  2. Remove the screen or aerator from the faucet (if applicable) and temporarily bypass whole home water softners or filters if you have them.
  3. Run the cold water only at full force for a few minutes until the water clears. Once it does, replace the faucet screen/aerator and put any bypass filters or softners back in service (if applicable).
  4. If your water doesn't clear after a few minutes, call us at (608) 837-5500.
  5. If you have lower pressure than usual at a faucet, remove the screen or aerator to check if it's clogged. If it is clogged and doesn't rinse easily, soak it in vinegar for at least 15 minutes and scrub it with an old tooth brush.
  6. If you have a water softener and are experiencing discolored water, place the unit into “regeneration or cleaning mode” after hydrant flushing is completed in your area.

We also suggest waiting until the evening to do laundry or run your dishwasher if we're flushing in your neighborhood - and make sure your water is clear before starting these tasks. Discolored water can stain clothes and porcelain.

Is the water safe to drink while flushing?

Yes, discolored water is safe to drink

While low concentrations of minerals are harmless, they can discolor the water and cause concern about the water quality. Sun Prairie’s low iron means there is not much iron to flush out, but caution should still be exercised when running loads of laundry.

My laundry is stained, what do I do now?

Keep the laundry wet and use an iron or stain-removing product like “Iron Out” rust and stain remover.

How often do water mains need to be flushed? 

Sun Prairie Utilities flushes hydrants at least every other year as required by Wisconsin State code NR 810.13. In areas where water may move more slowly through the system, such as hydrants located on a dead-end main, hydrants are flushed twice annually to maintain water quality.

How long does it take?

Sun Prairie has approximately 1,800 public fire hydrants to flush and it takes quite a while to operate and inspect each hydrant. Typically, flushing takes place April through October each year. Flushing is worked into our crew's schedule based on weather, staffing levels, and other scheduled work so it is difficult to provide a schedule with specific dates or times.

What if I have other questions? 

For more information, contact Sun Prairie Utilities at information@myspu.org or (608) 837-5500.